In their last eight starts, dating back to the beginning of June, both pitchers have been very good. Player A has been all but impossible to beat, having completed almost every game he's started, and going fewer than eight innings only once, when he went seven. He almost never walks anyone, generally keeps the ball in the yard, strikes batters out...everything you could want in a pitcher.

Player B, while not such a workhorse, has still been very effective. His team has gone 5-3 in those eight games, with him getting the win in four of those five. He strikes batters out just as often as Player A, and is just slightly more parsimonious when it comes to round-trippers. He's got very good control, too, though not the insanely low walk rate that Player A shows.

It's also worth noting that Player A has faced much stiffer competition than Player B. His eight starts have come against teams averaging 4.58 runs per game, while Player B's opponents have averaged only 3.96 runs per game so far in 2010.

Player A's opponents have included five of the six division winners and another team within two games of its division lead. Player B's opponents have included three of the six teams bringing up the rears of their divisions (two starts against one of the bottom-feeders), plus two teams within the bottom three in run-scoring in their leagues. Only one team with a winning record was in that group.

Player A, as you probably know, is Mariners' ace starter and top prize of this year's trading deadline market, Cliff Lee. He's awesome. No doubt about it. He automatically makes the Texas Rangers better, prohibitive favorites to win the AL West. They gave up a lot of talent to get him, but it should be worth it this year, at least.

But Player B, as you probably don't realize, is Javier Vazquez, who would seem to have been the odd man out if the Yankees had dealt for Lee last week, as was so widely rumored. The Yankees have set a limit on Phil Hughes' innings for 2010 -probably around 175.

Andy Pettitte, being 38 years old - and frankly, never this good before - is not likely to win another 11 games in the second half. I still expect him to pitch reasonably well and to be part of the postseason rotation, but of course you've gotta get there first, and the Rays and Sawx aren't exactly going away.

That leaves Pettitte, CC Sabathia and (come playoff time) two huge question marks in the rotation.

Of course Vazquez was atrocious in his first month or so of the season, as I mentioned, but he seems to have gotten back whatever it was that deserted him for the first month of the 2010 season, and has been as good as anybody for the last six weeks or so. Well, anybody but Cliff Lee, I suppose.

But how much better would swapping out Vazquez for Lee really have made the Yankees? At their current rates, over the remainder of the season, Lee could be expected to be pitch about 14 more times, around 119 innings at the rate noted above, and allow about 30 earned runs.

Vazquez projects for only 93 innings and about 26 earned runs. That's four runs difference, but in 26 fewer innings, and those of course would fall to the Yankees' bullpen. That bullpen has thus far allowed 103 runs in 224 innings in 2010, so at that rate they'd be expected to allow about 12 runs in 26 innings. So now Lee is better than Javy and the bullpen by a mere eight runs.

Except that in reality, the Lee will not finish nearly every game for the rest of the season. Indeed, pitching away from the cavernous, offense-depressing SafeCo Field, he would presumably give up a couple of runs once in a while and perhaps occasionally need to come out in (gasp!) the sixth inning.

So let's say that Lee throws 20 more innings than Vazquez over the second half instead of 26, still a generous improvement. In those 20 innings, the bullpen will probably allow about nine runs. Subtract from those the four runs that Vazquez "saved" by not pitching as much, and now Lee is worth a meager five runs more than Vazquez, given these assumptions. Given the aforementioned difference in qualities of their opponents we'll be magnanimous and say that Lee is really worth 10 runs.

Additionally, Lee and vazquez have both had unsustainably low batting averages on balls in play in that span. Lee's was .259, while Javy's was .192(!), and therefore clearly likely to bounce back to more normal ~.300ish levels. S, just for the heck of it, let's account for that differenc ewith an additional 10 runs, giving us 20 total.

Are 20 runs over the second half of the 2010 season worth, say, Jesus Montero, Mark Melancon and David Adams, names that were rumored in the deal the Yankees considered? Are 20 runs even worth a journeyman reliever and a bucket of used baseballs? Well, yes, in a close race.

More to the point, you're probably thinking, "It depends on which runs," and you're right. Lee helps a team win both by the innings he pitches and by those he prevents the bullpen from pitching, both by preventing runs from scoring and by allowing the offense to win without the pressure of having to score eight runs every night.

If the runs he saves are those that make a difference in getting the team into the playoffs, then they're worth just about any trade. If he then makes the difference in getting the team to later tiers of the playoffs and even to winning the World Series, then the trade is really worthwhile.

Do you think the Blue Jays and their fans mind that they traded away Jeff Kent to get David Cone in 1992, given that he pitched well down the stretch that year and helped them win their first-ever World Series? I doubt it. I know that Yankee fans would not ultimately have cared much if Marty Janzen or Mike Gordon or Jason Jarvis had become stars.

Those trading chips got the Yankees to the Promised Land in 1996, and helped cement Cone's place in Yankee history, winning four world championships. Nobody would have lamented the loss of prospects, even ones who blossom in another uniform, if it meant a 28th World Series title.

As it is, since the Rangers gave up a lot of prospects - who may not only eventually thrive, but may do so for a division rival - they'll have a lot of 'splainin to do if they miss the playoffs, or get ousted in the first round. For the Yankees and their fans, at least, they can take some solace in the hope that Lee would not have been such an incredible improvement over the man currently holding that spot in the rotation, Javy Vazquez, if all goes well.